[swift-users] libswiftCore.dylib was compiled with optimization - stepping may behave oddly;

[David Liu]

Thank you Michael this really helps a lot, i really appreciate your help.
Here is the bug i filed. https://bugs.swift.org/browse/SR-2494 .
Also as a side question, this is my current method of trying to debug the
Standard Library,  was wondering is there a better way to debug other than
build toolchain and debug through command line?

Cheers

Dave


On Thu, Aug 25, 2016 at 11:31 PM, Michael Gottesman <mgottesman at apple.com>
wrote:

> If you are using the build-toolchain command, the stdlib will be built
> with optimizations enabled [as one would hope when you compile a toolchain
> = )].
>
> If you want to have a debug stdlib, you need to make sure that the cmake
> flag -DSWIFT_STDLIB_BUILD_TYPE=Debug is set. (And probably you also want)
> -DSWIFT_STDLIB_ASSERTIONS=true.
>
> Now you are not going to be able to get that from build-toolchain without
> modification. A few thoughts:
>
> 1. I would file a bug on bugs.swift.org saying that you want the ability
> to tell build-toolchain to build a debug standard library. I think that is
> a reasonable request. Please respond to this thread with the URL.
> 2. Notice that the build-toolchain script has a build-script invocation
> inside of it. There is an option to build-script called something along the
> lines of --expand-build-script-command-line perhaps? Look for expand in
> the --help. You can add that to the script to grab the internal
> build-script invocation. Then add to the end of that invocation the option:
> --debug-swift-stdlib --swift-stdlib-assertions. Keep in mind that this is
> just from memory so you may need to munge it a little bit.
>
> Michael
>
> On Aug 26, 2016, at 12:36 AM, David Liu via swift-users <
> swift-users at swift.org> wrote:
>
> Hi all,  can any one here give me some pointers on debugging the standard
> library?
> I may be compiling the toolchain incorrectly when i step through the code
> variables on the stack frame are not available.
> I think its due to this message when i start the REPL
> `libswiftCore.dylib was compiled with optimization - stepping may behave
> oddly; variables may not be available.`
> I am using the /utils/build-toolchain command and did not touch the
> presets.ini file.
> Any help is appreciated!
>
> Thanks in advance
>
> Dave
>
> Process 13833 stopped
> * thread #1: tid = 0x3a6ffe, 0x00000001000c3603 libswiftCore.dylib`
> ManagedBufferPointer.init(_uncheckedBufferClass : AnyObject.Type,
> minimumCapacity : Int) -> ManagedBufferPointer<A, B> [inlined]
> Swift._roundUp (Swift.Int, toAlignment : Swift.Int) -> Swift.Int at
> Builtin.swift:72, queue = 'com.apple.main-thread', stop reason = step in
>     frame #0: 0x00000001000c3603 libswiftCore.dylib`
> ManagedBufferPointer.init(_uncheckedBufferClass : AnyObject.Type,
> minimumCapacity : Int) -> ManagedBufferPointer<A, B> [inlined]
> Swift._roundUp (Swift.Int, toAlignment : Swift.Int) -> Swift.Int at
> Builtin.swift:72 [opt]
>    69  @_versioned
>    70  internal func _roundUp(_ offset: Int, toAlignment alignment: Int)
> -> Int {
>    71    _sanityCheck(offset >= 0)
> -> 72    return Int(_roundUpImpl(UInt(bitPattern: offset), toAlignment:
> alignment))
>    73  }
>    74
>    75  // This function takes a raw pointer and returns a typed pointer.
> It implicitly
> (lldb) fr v
> (lldb) po offset
> error: <EXPR>:3:1: error: use of unresolved identifier 'offset'
> offset
> ^~~~~~
> (lldb) fr v offset
> error: no variable named 'offset' found in this frame
> (lldb) s
> Process 13833 stopped
> * thread #1: tid = 0x3a6ffe, 0x00000001000c3603 libswiftCore.dylib`
> ManagedBufferPointer.init(_uncheckedBufferClass : AnyObject.Type,
> minimumCapacity : Int) -> ManagedBufferPointer<A, B> [inlined]
> Swift._roundUpImpl (Swift.UInt, toAlignment : Swift.Int) -> Swift.UInt at
> Builtin.swift:58, queue = 'com.apple.main-thread', stop reason = step in
>     frame #0: 0x00000001000c3603 libswiftCore.dylib`
> ManagedBufferPointer.init(_uncheckedBufferClass : AnyObject.Type,
> minimumCapacity : Int) -> ManagedBufferPointer<A, B> [inlined]
> Swift._roundUpImpl (Swift.UInt, toAlignment : Swift.Int) -> Swift.UInt at
> Builtin.swift:58 [opt]
>    55    _sanityCheck(_isPowerOf2(alignment))
>    56    // Note, given that offset is >= 0, and alignment > 0, we don't
>    57    // need to underflow check the -1, as it can never underflow.
> -> 58    let x = offset + UInt(bitPattern: alignment) &- 1
>    59    // Note, as alignment is a power of 2, we'll use masking to
> efficiently
>    60    // get the aligned value
>    61    return x & ~(UInt(bitPattern: alignment) &- 1)
> (lldb) fr v
> (lldb) fr v -R
> (lldb) fr v aligment
> error: no variable named 'aligment' found in this frame
> (lldb) fr v alignment
> error: no variable named 'alignment' found in this frame
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